1. Field of the Invention
Embodiments of the present invention generally relate to methods for forming a microcrystalline silicon film. More particularly, this invention relates to methods for forming a microcrystalline silicon film in thin film transistors devices.
2. Description of the Related Art
Plasma display panels and liquid crystal displays are frequently used for flat panel displays. Liquid crystal displays (LCD) generally contain two glass substrates joined together with a layer of a liquid crystal material sandwiched therebetween. The glass substrate may be a semiconductor substrate, or may be a transparent substrate such as a glass, quartz, sapphire, or a clear plastic film. The LCD may also contain light emitting diodes for back lighting.
As the resolution requirements for liquid crystal displays increase, it has become desirable to control a large number of separate areas of the liquid crystal cell, called pixels. In a modern display panel, more than 1,000,000 pixels may be present. At least the same number of transistors is formed on the glass substrate so that each pixel can be switched between an energized and de-energized state relative to the other pixels disposed on the substrate.
FIG. 1 depicts a conventional thin film transistor device 100 disposed on a substrate 102. A dielectric layer 104 may be optionally disposed on the substrate 102. Subsequently, a gate electrode 106 is formed and patterned on the dielectric layer 104 followed by a gate insulator layer 108. A semiconductor layer of amorphous silicon (a-Si) 110 is usually formed on the gate insulator layer 108 followed by a thin doped semiconductor layer of n-type or p-type amorphous silicon layer (N+/P+-a-Si) 112. After formation of the doped semiconductor layer 112, a source-drain metal electrode layer 114 is then disposed thereon to form the thin film transistor device 100. Since electron mobility in the transistors dominates device performance, greater mobility of electrons in transistors or devices is often desired. A electronic device with high electron mobility would allow more pixel area for light transmission and integration of circuitry, thereby allowing brighter display, higher overall electrical efficiency, faster response time and higher resolution displays. The limited electron mobility inherent to conventionally processed amorphous silicon device results in limited frame refresh rates and pixel densities. Moreover, a stable and reliable operation of electronic devices with lower threshold voltage shift also prevail the overall performance of the electronic devices.
Therefore, there is a need for devices having improved electron mobility and stability and a method for manufacturing the same.